Research On Optical Surface Clean With Air Knife Purge Technology

High energy laser driver is a core part of laser inertial confinement fusion device, the final optical assembly(FOA for short) which integrates multiple high-value large aperture optical elements is at the end of the driver, and its main function is to achieve the laser’s frequency conversion and precise focusing. The surface cleanliness of optics is the main reason for opti cal elements damage in high energy laser driver, also is the biggest obstacle to improve the load capacity of driver. In this paper, China’s largest inertial confinement fusion device–the host device of SG-Ⅲ final optical assembly of the host device as the research object, the study of obtaining and maintaining techniques about the surface cleanliness of optical elements based on air knife was carried out, to achieve long-term stable running of the FOA.Firstly, based on fluid dynamics theory, the concerned problems of using high-speed air stream to remove the surface particles on optical elements were analyzed. Combined with discrete element method and fluid analysis technology, the gal-solid phase flow analysis model to remove adhesive particles based on air knife was built.Then, the source and influence law of the adhesive force to solid particles were analyzed, and the adhesive force of different sizes of particles on the optical surface was calculated, in addition, a model for calculating the solid particles’ adhesive force on optical surface was established. Through building a calculating model of air knife gas pressure distribution, the effectiveness about the gas dynamic pressure of the optical surface to remove the adhesive particles was analyzed theoretically.Using Fluent and EDEM software, the fluid-solid coupling simulation model based on air knife sweeping system was built, and the sweeping process of the optical surface adhesive particles was simulated, then the removal law and rate of the air knife sweeping parameters for adhesive particles were obtained; and the wind screen formation of optical elements surface based on air knife and isolation process to foreign particles were simulated and analyzed, the isolation laws of air knife parameters on foreign particles were obtained.Finally, the simplified experimental program about cleanliness sweeping and protecting system based on air knife was designed, and the experiments on particle sweeping and wind screen isolation to the optical surface were made, the accuracy of the simulation was tested, the conclusion that the air knife sweeping system enables remove adhesive particles that diameter are between 5~90μm and enables isolate the foreign particles within the range and it can be used for online cleaning of the optical element surface in terminal components was drawn.